Insulators for high voltage electrical transmission lines may take many forms. In recent years, composite insulators have become extremely popular. One such insulator comprises a rod fabricated of glass fiber impregnated with an organic binder. The rod is coated with a rubber insulating sheath and a plurality of rubber weathersheds are spaced along the rod and fastened to the sheath.
A composite insulator of this type normally has a high voltage electrode fitting fastened to the sheathed rod at one and a ground fitting fastened to the sheathed rod at the other end. Field experience has shown that the rubber sheath in the vicinity of the high voltage electrode end fitting can be susceptible to aging and/or erosion due to surface electrical discharges that can occur where extremely contaminated conditions exist.